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Hasina 2,990

The heat released by everyday activities in energy-guzzling cities is changing the weather in far-away places, scientists report today (Jan. 27).

The released heat is changing temperatures in areas more than 1,000 miles away (1609 kilometers). It is warming parts of North America by about 1 degree Fahrenheit (0.6 degrees Celsius) and northern Asia by as much as 1.8 degrees Fahrenheit (1 degree Celsius), while cooling areas of Europe by a similar amount, scientists report in the journal Nature Climate Change.

The released heat (dubbed waste heat), it seems, is changing atmospheric circulation, including jet streams — powerful narrow currents of wind that blow from west to east and north to south in the upper atmosphere.

This impact on regional temperatures may explain a climate puzzle of sorts: why some areas are having warmer winters than predicted by climate models, the researchers said. In turn, the results suggest this phenomenon should be accounted for in models forecasting global warming.

"There's a tendency in climate science to overlook the effects of cities," Brian Stone, a professor of city and regional planning at Georgia Tech, told LiveScience. "Cities occupy just a few percent of the land surface, but the amount of energy released as waste heat is contributing downwind to pretty significant changes in climate. I hope this will encourage us to focus more on cities as important drivers of climate change," added Stone, who was not involved in the current study.

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questionmark 11,353

Correct, and if we talk about cities in the USA that is partly because most of the interior heating ends up in the exterior, thereby changing the micro climate, and with it, albeit in a small faction, the whole climate.

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questionmark 11,353

As the increase in global temperatures is very small (faction of a degree annually) could the Urban Heat Island effect account for all of the measured global warming ?

I doubt it, while the temperature difference between the city and the surrounding free land may be significant it hardly gets out of its confines. And to that, we always have to think that solar irradiation, even in winter in the north is around 2-3 KW/h per square meter and around 5-6 KW/h in summer. We would need a few more megawatt electric plants to achieve the same effect...per city, naturally.

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Ashotep 13,706

I have friends that live in a town of about 20,000 and they say they can notice a difference in the temperature when they come to my house about 30 miles away. In the summer they think its nice but in the winter they complain.